984 TRACHEA 
excepted, a single ampulla often of considerable size being thrown 
out on one side—usually the left. This structure obtains ap- 
parently throughout all the “Freshwater Ducks” or Anatiny, as 
well as in Somateria and Tachyeres, but it is subject to great 
exaggeration and, though occasionally absent as in Gdemia, becomes 
very complicated in the group of “Diving Ducks,” forming 
in many cases a tympanum, whose bony walls are fenestrated and 
the spaces filled with a resonant membrane,! while it attains its 
ereatest magnitude in the Merging. Tudorna has two bony ampullz, 
one on each side, and dilatations are also present in Chenalopea, 
Sarcidiornis and, according to Eyton (op. cit. p. 83, pl. i. figs. 1, 2), 
in Chloephaga magellanica. In Dendrocygna the labyrinth is com- 
posed of two oblong chambers, and takes the form of a symmetrical 
shield-shaped box ([bis, 1859, p. 366). 
Quite as remarkable is the lengthening of the Trachea in some 
birds during adolescence, so that to be contained conveniently it is 
looped, and this formation is frequently, though not always, con- 
fined to one or the other sex. In the male of Yetrao urogallus 
(CAPERCALLY) and in the female of Axnserunas there is a simple 
subcutaneous loop. In the female of the Old-World Painted 
SNIPES (p. 887), Lostrutula, the loop extends ventrally over the 
furcula, and more or less over the pectoral muscles (cf. Wood- 
Mason, Proc. Zool. Soc. 1878, p. 745), and a similar arrangement is 
found in the males of most Cracinx (CURASSOW), while it occurs in 
both sexes of Penelope jacucaca, though most of the Penelopine 
(GUAN) have no loop at all. Among Passeres a series of coils is 
found in both sexes of Phonygama, and in the males of Manucodia 
(MANucODE). In the male of Anseranas the convolutions of the 
Trachea lying outside the pectoral muscles are not only subject 
to variation in number, but they may be placed on either side of 
the body (cf. Yarrell, Zrans. Linn. Soc. xv. pp. 383, 384, pls. 
xii. xiv.), the form of the coracoid on that side being modified 
accordingly. A curious peculiarity is exhibited by the Crested 
GUINEA FOoOwLs (supra, p. 401), in both sexes of which the 
symphysis of the furcula is dilated so as to lodge a short tracheal 
loop (tom. cit. pl. ix.). 
The furcula and coracoids are not, however, the only bones 
which are modified by the excessive lengthening of the 7rachea. 
As has long been known, some of the SwANs and CRANES have 
their sternum invaded by it; but each in a different way—the 
1 Very remarkable is the tracheal structure of Harelda and Rhodonessa, but 
want of space renders it impossible to particularize all the pecullarities in this 
group of Anatide. Reference may be made to the classical papers of Latham and 
Yarrell (Zrans. Linn. Soc. iv. pp. 90-128, and xv. pp. 378-388), as well as to 
Kyton’s Afonograph above cited, and the observations of Garrod (Proc. Zool. Soa 
1875, pp. 151-156) and Forbes (op. cil. 1882, pp. 347-353). 
